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	$102.97	3.488%	$106.5616	$106.56	$106.55	$106.60
Purchase #2	$74.56	11.619%	$83.2231	$83.22	$83.20	$83.20
Purchase #3	$77.68	4.172%	$80.9208	$80.92	$80.90	$80.90
Purchase #4	$189.55	3.868%	$196.8818	$196.88	$196.90	$196.90
Purchase #5	$249.76	4.817%	$261.7909	$261.79	$261.80	$261.80
Purchase #6	$156.42	9.566%	$171.3831	$171.38	$171.40	$171.40
Purchase #7	$45.33	5.417%	$47.7855	$47.79	$47.80	$47.80
7 purchase totals =	$896.27		$948.5468	$948.54	$948.55	$948.60