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	$42.56	6.437%	$45.2996	$45.30	$45.30	$45.30
Purchase #2	$190.29	11.874%	$212.885	$212.89	$212.90	$212.90
Purchase #3	$98.29	11.666%	$109.7565	$109.76	$109.75	$109.80
Purchase #4	$226.28	7.632%	$243.5497	$243.55	$243.55	$243.50
Purchase #5	$189.90	8.543%	$206.1232	$206.12	$206.10	$206.10
Purchase #6	$113.40	10.354%	$125.1414	$125.14	$125.15	$125.10
Purchase #7	$45.81	9.404%	$50.118	$50.12	$50.10	$50.10
7 purchase totals =	$906.53		$992.8734	$992.88	$992.85	$992.80