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	$149.48	11.788%	$167.1007	$167.10	$167.10	$167.10
Purchase #2	$242.51	10.632%	$268.2937	$268.29	$268.30	$268.30
Purchase #3	$143.28	3.465%	$148.2447	$148.24	$148.25	$148.20
Purchase #4	$65.49	10.589%	$72.4247	$72.42	$72.40	$72.40
Purchase #5	$31.25	5.399%	$32.9372	$32.94	$32.95	$32.90
Purchase #6	$122.55	8.582%	$133.0672	$133.07	$133.05	$133.10
Purchase #7	$199.77	5.759%	$211.2748	$211.27	$211.25	$211.30
7 purchase totals =	$954.33		$1,033.3430	$1,033.33	$1,033.30	$1,033.30