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	$141.47	3.787%	$146.8275	$146.83	$146.85	$146.80
Purchase #2	$170.41	12.154%	$191.1216	$191.12	$191.10	$191.10
Purchase #3	$212.80	7.292%	$228.3174	$228.32	$228.30	$228.30
Purchase #4	$67.91	13.270%	$76.9217	$76.92	$76.90	$76.90
Purchase #5	$91.88	5.428%	$96.8672	$96.87	$96.85	$96.90
Purchase #6	$65.88	8.723%	$71.6267	$71.63	$71.65	$71.60
Purchase #7	$20.59	3.323%	$21.2742	$21.27	$21.25	$21.30
7 purchase totals =	$770.94		$832.9563	$832.96	$832.90	$832.90