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	$230.89	7.352%	$247.865	$247.87	$247.85	$247.90
Purchase #2	$215.86	3.171%	$222.7049	$222.70	$222.70	$222.70
Purchase #3	$66.33	9.166%	$72.4098	$72.41	$72.40	$72.40
Purchase #4	$78.80	8.132%	$85.208	$85.21	$85.20	$85.20
Purchase #5	$155.35	6.168%	$164.932	$164.93	$164.95	$164.90
Purchase #6	$127.98	5.508%	$135.0291	$135.03	$135.05	$135.00
Purchase #7	$152.30	6.288%	$161.8766	$161.88	$161.90	$161.90
7 purchase totals =	$1,027.51		$1,090.0254	$1,090.03	$1,090.05	$1,090.00