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	$174.41	4.857%	$182.8811	$182.88	$182.90	$182.90
Purchase #2	$54.52	12.333%	$61.244	$61.24	$61.25	$61.20
Purchase #3	$106.31	7.133%	$113.8931	$113.89	$113.90	$113.90
Purchase #4	$226.33	5.179%	$238.0516	$238.05	$238.05	$238.10
Purchase #5	$34.92	10.168%	$38.4707	$38.47	$38.45	$38.50
Purchase #6	$243.89	10.834%	$270.313	$270.31	$270.30	$270.30
Purchase #7	$239.46	12.144%	$268.54	$268.54	$268.55	$268.50
7 purchase totals =	$1,079.84		$1,173.3935	$1,173.38	$1,173.40	$1,173.40