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	$110.75	11.292%	$123.2559	$123.26	$123.25	$123.30
Purchase #2	$113.66	8.801%	$123.6632	$123.66	$123.65	$123.70
Purchase #3	$68.38	4.270%	$71.2998	$71.30	$71.30	$71.30
Purchase #4	$67.72	5.395%	$71.3735	$71.37	$71.35	$71.40
Purchase #5	$36.80	11.467%	$41.0199	$41.02	$41.00	$41.00
Purchase #6	$165.74	11.579%	$184.931	$184.93	$184.95	$184.90
Purchase #7	$118.84	5.505%	$125.3821	$125.38	$125.40	$125.40
7 purchase totals =	$681.89		$740.9254	$740.92	$740.90	$741.00