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	$56.58	9.376%	$61.8849	$61.88	$61.90	$61.90
Purchase #2	$172.47	5.589%	$182.1093	$182.11	$182.10	$182.10
Purchase #3	$85.98	4.360%	$89.7287	$89.73	$89.75	$89.70
Purchase #4	$236.49	9.477%	$258.9022	$258.90	$258.90	$258.90
Purchase #5	$217.59	4.206%	$226.7418	$226.74	$226.75	$226.70
Purchase #6	$198.38	11.610%	$221.4119	$221.41	$221.40	$221.40
Purchase #7	$58.64	11.152%	$65.1795	$65.18	$65.20	$65.20
7 purchase totals =	$1,026.13		$1,105.9583	$1,105.95	$1,106.00	$1,105.90