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	$42.96	5.374%	$45.2687	$45.27	$45.25	$45.30
Purchase #2	$78.41	3.123%	$80.8587	$80.86	$80.85	$80.90
Purchase #3	$156.69	13.671%	$178.1111	$178.11	$178.10	$178.10
Purchase #4	$148.61	5.488%	$156.7657	$156.77	$156.75	$156.80
Purchase #5	$105.69	5.418%	$111.4163	$111.42	$111.40	$111.40
Purchase #6	$197.59	6.463%	$210.3602	$210.36	$210.35	$210.40
Purchase #7	$110.72	4.327%	$115.5109	$115.51	$115.50	$115.50
7 purchase totals =	$840.67		$898.2916	$898.30	$898.20	$898.40