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	$168.84	9.709%	$185.2327	$185.23	$185.25	$185.20
Purchase #2	$59.30	3.468%	$61.3565	$61.36	$61.35	$61.40
Purchase #3	$66.61	9.415%	$72.8813	$72.88	$72.90	$72.90
Purchase #4	$167.43	4.311%	$174.6479	$174.65	$174.65	$174.60
Purchase #5	$142.44	5.582%	$150.391	$150.39	$150.40	$150.40
Purchase #6	$95.81	5.642%	$101.2156	$101.22	$101.20	$101.20
Purchase #7	$44.55	4.609%	$46.6033	$46.60	$46.60	$46.60
7 purchase totals =	$744.98		$792.3283	$792.33	$792.35	$792.30