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	$154.59	11.168%	$171.8546	$171.85	$171.85	$171.90
Purchase #2	$211.90	7.603%	$228.0108	$228.01	$228.00	$228.00
Purchase #3	$36.89	9.167%	$40.2717	$40.27	$40.25	$40.30
Purchase #4	$95.48	8.142%	$103.254	$103.25	$103.25	$103.30
Purchase #5	$236.91	11.407%	$263.9343	$263.93	$263.95	$263.90
Purchase #6	$181.25	5.674%	$191.5341	$191.53	$191.55	$191.50
Purchase #7	$64.31	4.872%	$67.4432	$67.44	$67.45	$67.40
7 purchase totals =	$981.33		$1,066.3027	$1,066.28	$1,066.30	$1,066.30