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	$84.74	13.380%	$96.0782	$96.08	$96.10	$96.10
Purchase #2	$154.51	8.156%	$167.1118	$167.11	$167.10	$167.10
Purchase #3	$18.71	11.309%	$20.8259	$20.83	$20.85	$20.80
Purchase #4	$246.73	6.359%	$262.4196	$262.42	$262.40	$262.40
Purchase #5	$149.62	4.764%	$156.7479	$156.75	$156.75	$156.70
Purchase #6	$34.88	7.316%	$37.4318	$37.43	$37.45	$37.40
Purchase #7	$51.75	6.112%	$54.913	$54.91	$54.90	$54.90
7 purchase totals =	$740.94		$795.5282	$795.53	$795.55	$795.40