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	$82.76	12.275%	$92.9188	$92.92	$92.90	$92.90
Purchase #2	$233.53	7.465%	$250.963	$250.96	$250.95	$251.00
Purchase #3	$90.61	5.196%	$95.3181	$95.32	$95.30	$95.30
Purchase #4	$238.33	9.873%	$261.8603	$261.86	$261.85	$261.90
Purchase #5	$151.57	9.104%	$165.3689	$165.37	$165.35	$165.40
Purchase #6	$223.26	4.807%	$233.9921	$233.99	$234.00	$234.00
Purchase #7	$87.28	10.117%	$96.1101	$96.11	$96.10	$96.10
7 purchase totals =	$1,107.34		$1,196.5313	$1,196.53	$1,196.45	$1,196.60