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	$181.84	5.753%	$192.3013	$192.30	$192.30	$192.30
Purchase #2	$211.48	11.535%	$235.8742	$235.87	$235.85	$235.90
Purchase #3	$54.77	9.145%	$59.7787	$59.78	$59.80	$59.80
Purchase #4	$158.27	12.683%	$178.3434	$178.34	$178.35	$178.30
Purchase #5	$118.33	7.737%	$127.4852	$127.49	$127.50	$127.50
Purchase #6	$107.56	5.701%	$113.692	$113.69	$113.70	$113.70
Purchase #7	$179.29	5.574%	$189.2836	$189.28	$189.30	$189.30
7 purchase totals =	$1,011.54		$1,096.7584	$1,096.75	$1,096.80	$1,096.80