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	$83.41	8.560%	$90.5499	$90.55	$90.55	$90.50
Purchase #2	$91.52	9.198%	$99.938	$99.94	$99.95	$99.90
Purchase #3	$23.33	6.495%	$24.8453	$24.85	$24.85	$24.80
Purchase #4	$240.50	3.667%	$249.3191	$249.32	$249.30	$249.30
Purchase #5	$110.73	3.129%	$114.1947	$114.19	$114.20	$114.20
Purchase #6	$98.55	3.557%	$102.0554	$102.06	$102.05	$102.10
Purchase #7	$58.78	10.773%	$65.1124	$65.11	$65.10	$65.10
7 purchase totals =	$706.82		$746.0148	$746.02	$746.00	$745.90