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	$174.40	3.842%	$181.1004	$181.10	$181.10	$181.10
Purchase #2	$105.79	3.534%	$109.5286	$109.53	$109.55	$109.50
Purchase #3	$127.28	3.636%	$131.9079	$131.91	$131.90	$131.90
Purchase #4	$181.65	12.684%	$204.6905	$204.69	$204.70	$204.70
Purchase #5	$239.82	5.613%	$253.2811	$253.28	$253.30	$253.30
Purchase #6	$51.83	4.412%	$54.1167	$54.12	$54.10	$54.10
Purchase #7	$123.82	5.148%	$130.1943	$130.19	$130.20	$130.20
7 purchase totals =	$1,004.59		$1,064.8195	$1,064.82	$1,064.85	$1,064.80