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	$237.83	11.327%	$264.769	$264.77	$264.75	$264.80
Purchase #2	$248.96	5.186%	$261.8711	$261.87	$261.85	$261.90
Purchase #3	$115.37	6.614%	$123.0006	$123.00	$123.00	$123.00
Purchase #4	$108.96	10.191%	$120.0641	$120.06	$120.05	$120.10
Purchase #5	$53.68	9.243%	$58.6416	$58.64	$58.65	$58.60
Purchase #6	$93.53	9.375%	$102.2984	$102.30	$102.30	$102.30
Purchase #7	$72.39	13.715%	$82.3183	$82.32	$82.30	$82.30
7 purchase totals =	$930.72		$1,012.9631	$1,012.96	$1,012.90	$1,013.00