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	$109.91	3.820%	$114.1086	$114.11	$114.10	$114.10
Purchase #2	$51.91	4.794%	$54.3986	$54.40	$54.40	$54.40
Purchase #3	$40.62	6.687%	$43.3363	$43.34	$43.35	$43.30
Purchase #4	$194.43	9.439%	$212.7822	$212.78	$212.80	$212.80
Purchase #5	$134.78	11.318%	$150.0344	$150.03	$150.05	$150.00
Purchase #6	$224.74	6.871%	$240.1819	$240.18	$240.20	$240.20
Purchase #7	$78.68	13.114%	$88.9981	$89.00	$89.00	$89.00
7 purchase totals =	$835.07		$903.8401	$903.84	$903.90	$903.80