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	$170.81	8.299%	$184.9855	$184.99	$185.00	$185.00
Purchase #2	$175.80	8.501%	$190.7448	$190.74	$190.75	$190.70
Purchase #3	$159.98	8.740%	$173.9623	$173.96	$173.95	$174.00
Purchase #4	$126.54	4.106%	$131.7357	$131.74	$131.75	$131.70
Purchase #5	$102.98	6.177%	$109.3411	$109.34	$109.35	$109.30
Purchase #6	$227.38	9.562%	$249.1221	$249.12	$249.10	$249.10
Purchase #7	$66.77	7.673%	$71.8933	$71.89	$71.90	$71.90
7 purchase totals =	$1,030.26		$1,111.7848	$1,111.78	$1,111.80	$1,111.70