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	$62.87	6.670%	$67.0634	$67.06	$67.05	$67.10
Purchase #2	$40.31	4.815%	$42.2509	$42.25	$42.25	$42.30
Purchase #3	$245.80	12.220%	$275.8368	$275.84	$275.85	$275.80
Purchase #4	$116.35	11.607%	$129.8547	$129.85	$129.85	$129.90
Purchase #5	$189.91	13.649%	$215.8308	$215.83	$215.85	$215.80
Purchase #6	$202.48	11.781%	$226.3342	$226.33	$226.35	$226.30
Purchase #7	$181.39	5.702%	$191.7329	$191.73	$191.75	$191.70
7 purchase totals =	$1,039.11		$1,148.9037	$1,148.89	$1,148.95	$1,148.90