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	$180.69	8.210%	$195.5246	$195.52	$195.50	$195.50
Purchase #2	$110.59	11.593%	$123.4107	$123.41	$123.40	$123.40
Purchase #3	$162.88	7.695%	$175.4136	$175.41	$175.40	$175.40
Purchase #4	$57.47	4.260%	$59.9182	$59.92	$59.90	$59.90
Purchase #5	$192.28	12.354%	$216.0343	$216.03	$216.05	$216.00
Purchase #6	$207.97	10.292%	$229.3743	$229.37	$229.35	$229.40
Purchase #7	$49.31	3.649%	$51.1093	$51.11	$51.10	$51.10
7 purchase totals =	$961.19		$1,050.7850	$1,050.77	$1,050.70	$1,050.70