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	$172.71	7.289%	$185.2988	$185.30	$185.30	$185.30
Purchase #2	$195.33	4.661%	$204.4343	$204.43	$204.45	$204.40
Purchase #3	$61.54	11.818%	$68.8128	$68.81	$68.80	$68.80
Purchase #4	$226.56	11.732%	$253.14	$253.14	$253.15	$253.10
Purchase #5	$184.33	6.437%	$196.1953	$196.20	$196.20	$196.20
Purchase #6	$47.75	10.617%	$52.8196	$52.82	$52.80	$52.80
Purchase #7	$188.50	9.315%	$206.0588	$206.06	$206.05	$206.10
7 purchase totals =	$1,076.72		$1,166.7596	$1,166.76	$1,166.75	$1,166.70