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	$143.61	10.485%	$158.6675	$158.67	$158.65	$158.70
Purchase #2	$76.27	7.547%	$82.0261	$82.03	$82.05	$82.00
Purchase #3	$88.92	9.751%	$97.5906	$97.59	$97.60	$97.60
Purchase #4	$97.86	6.645%	$104.3628	$104.36	$104.35	$104.40
Purchase #5	$111.64	10.279%	$123.1155	$123.12	$123.10	$123.10
Purchase #6	$173.33	11.874%	$193.9112	$193.91	$193.90	$193.90
Purchase #7	$92.72	13.717%	$105.4384	$105.44	$105.45	$105.40
7 purchase totals =	$784.35		$865.1121	$865.12	$865.10	$865.10