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	$62.97	13.277%	$71.3305	$71.33	$71.35	$71.30
Purchase #2	$100.26	5.376%	$105.65	$105.65	$105.65	$105.70
Purchase #3	$98.91	10.378%	$109.1749	$109.17	$109.15	$109.20
Purchase #4	$60.92	5.774%	$64.4375	$64.44	$64.45	$64.40
Purchase #5	$57.69	4.463%	$60.2647	$60.26	$60.25	$60.30
Purchase #6	$156.83	7.158%	$168.0559	$168.06	$168.05	$168.10
Purchase #7	$142.99	5.138%	$150.3368	$150.34	$150.35	$150.30
7 purchase totals =	$680.57		$729.2503	$729.25	$729.25	$729.30