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	$171.28	10.217%	$188.7797	$188.78	$188.80	$188.80
Purchase #2	$181.84	11.650%	$203.0244	$203.02	$203.00	$203.00
Purchase #3	$51.35	3.376%	$53.0836	$53.08	$53.10	$53.10
Purchase #4	$198.92	11.662%	$222.1181	$222.12	$222.10	$222.10
Purchase #5	$100.58	4.453%	$105.0588	$105.06	$105.05	$105.10
Purchase #6	$33.88	11.446%	$37.7579	$37.76	$37.75	$37.80
Purchase #7	$235.98	9.505%	$258.4099	$258.41	$258.40	$258.40
7 purchase totals =	$973.83		$1,068.2324	$1,068.23	$1,068.20	$1,068.30