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	$246.40	7.299%	$264.3847	$264.38	$264.40	$264.40
Purchase #2	$59.57	8.284%	$64.5048	$64.50	$64.50	$64.50
Purchase #3	$223.72	6.453%	$238.1567	$238.16	$238.15	$238.20
Purchase #4	$202.50	9.354%	$221.4419	$221.44	$221.45	$221.40
Purchase #5	$50.59	12.386%	$56.8561	$56.86	$56.85	$56.90
Purchase #6	$229.40	9.158%	$250.4085	$250.41	$250.40	$250.40
Purchase #7	$15.33	6.424%	$16.3148	$16.31	$16.30	$16.30
7 purchase totals =	$1,027.51		$1,112.0675	$1,112.06	$1,112.05	$1,112.10