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	$204.41	9.148%	$223.1094	$223.11	$223.10	$223.10
Purchase #2	$81.49	11.864%	$91.158	$91.16	$91.15	$91.20
Purchase #3	$84.61	9.419%	$92.5794	$92.58	$92.60	$92.60
Purchase #4	$213.90	4.635%	$223.8143	$223.81	$223.80	$223.80
Purchase #5	$74.40	8.553%	$80.7634	$80.76	$80.75	$80.80
Purchase #6	$206.80	12.695%	$233.0533	$233.05	$233.05	$233.10
Purchase #7	$113.32	9.107%	$123.6401	$123.64	$123.65	$123.60
7 purchase totals =	$978.93		$1,068.1179	$1,068.11	$1,068.10	$1,068.20