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	$172.90	11.689%	$193.1103	$193.11	$193.10	$193.10
Purchase #2	$59.97	9.153%	$65.4591	$65.46	$65.45	$65.50
Purchase #3	$89.84	7.221%	$96.3273	$96.33	$96.35	$96.30
Purchase #4	$17.89	6.824%	$19.1108	$19.11	$19.10	$19.10
Purchase #5	$221.43	3.819%	$229.8864	$229.89	$229.90	$229.90
Purchase #6	$98.54	7.106%	$105.5423	$105.54	$105.55	$105.50
Purchase #7	$39.28	7.220%	$42.116	$42.12	$42.10	$42.10
7 purchase totals =	$699.85		$751.5522	$751.56	$751.55	$751.50