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	$97.81	11.635%	$109.1902	$109.19	$109.20	$109.20
Purchase #2	$99.68	6.817%	$106.4752	$106.48	$106.50	$106.50
Purchase #3	$91.45	3.388%	$94.5483	$94.55	$94.55	$94.50
Purchase #4	$201.81	10.652%	$223.3068	$223.31	$223.30	$223.30
Purchase #5	$92.43	4.726%	$96.7982	$96.80	$96.80	$96.80
Purchase #6	$27.77	12.817%	$31.3293	$31.33	$31.35	$31.30
Purchase #7	$170.77	11.704%	$190.7569	$190.76	$190.75	$190.80
7 purchase totals =	$781.72		$852.4049	$852.42	$852.45	$852.40