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	$111.39	3.454%	$115.2374	$115.24	$115.25	$115.20
Purchase #2	$121.89	10.854%	$135.1199	$135.12	$135.10	$135.10
Purchase #3	$170.28	4.685%	$178.2576	$178.26	$178.25	$178.30
Purchase #4	$81.31	9.741%	$89.2304	$89.23	$89.25	$89.20
Purchase #5	$67.32	8.263%	$72.8827	$72.88	$72.90	$72.90
Purchase #6	$138.35	9.202%	$151.081	$151.08	$151.10	$151.10
Purchase #7	$235.64	10.632%	$260.6932	$260.69	$260.70	$260.70
7 purchase totals =	$926.18		$1,002.5022	$1,002.50	$1,002.55	$1,002.50