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	$124.74	7.183%	$133.7001	$133.70	$133.70	$133.70
Purchase #2	$49.88	3.815%	$51.7829	$51.78	$51.80	$51.80
Purchase #3	$140.63	6.709%	$150.0649	$150.06	$150.05	$150.10
Purchase #4	$148.78	11.649%	$166.1114	$166.11	$166.10	$166.10
Purchase #5	$59.90	13.198%	$67.8056	$67.81	$67.80	$67.80
Purchase #6	$174.97	7.744%	$188.5197	$188.52	$188.50	$188.50
Purchase #7	$85.99	12.697%	$96.9082	$96.91	$96.90	$96.90
7 purchase totals =	$784.89		$854.8928	$854.89	$854.85	$854.90