Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$218.39	7.499%	$234.7671	$234.77	$234.75	$234.80
Purchase #2	$125.83	5.229%	$132.4097	$132.41	$132.40	$132.40
Purchase #3	$71.61	7.604%	$77.0552	$77.06	$77.05	$77.10
Purchase #4	$240.29	11.777%	$268.589	$268.59	$268.60	$268.60
Purchase #5	$191.59	11.322%	$213.2818	$213.28	$213.30	$213.30
Purchase #6	$186.72	6.645%	$199.1275	$199.13	$199.15	$199.10
Purchase #7	$56.61	4.837%	$59.3482	$59.35	$59.35	$59.30
7 purchase totals =	$1,091.04		$1,184.5785	$1,184.59	$1,184.60	$1,184.60