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	$147.65	12.154%	$165.5954	$165.60	$165.60	$165.60
Purchase #2	$136.88	13.519%	$155.3848	$155.38	$155.40	$155.40
Purchase #3	$13.32	9.670%	$14.608	$14.61	$14.60	$14.60
Purchase #4	$210.94	10.817%	$233.7574	$233.76	$233.75	$233.80
Purchase #5	$86.70	13.456%	$98.3664	$98.37	$98.35	$98.40
Purchase #6	$219.46	6.591%	$233.9246	$233.92	$233.90	$233.90
Purchase #7	$195.90	8.289%	$212.1382	$212.14	$212.15	$212.10
7 purchase totals =	$1,010.85		$1,113.7748	$1,113.78	$1,113.75	$1,113.80