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	$174.30	5.484%	$183.8586	$183.86	$183.85	$183.90
Purchase #2	$51.64	5.144%	$54.2964	$54.30	$54.30	$54.30
Purchase #3	$223.65	12.447%	$251.4877	$251.49	$251.50	$251.50
Purchase #4	$243.41	4.658%	$254.748	$254.75	$254.75	$254.70
Purchase #5	$6.91	6.805%	$7.3802	$7.38	$7.40	$7.40
Purchase #6	$92.30	13.192%	$104.4762	$104.48	$104.50	$104.50
Purchase #7	$91.62	13.355%	$103.8559	$103.86	$103.85	$103.90
7 purchase totals =	$883.83		$960.1030	$960.12	$960.15	$960.20